Method of oxidizing materials in electric furnaces



W. S. MAYER AND W, C. KENNEDY.

METHOD 0E oxIDIzING MATERIALS III ELECTRIC TURN/ICES.

1,350,877' APPLICATION FILED MAR. I7, 19H. Aug. 24,

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INvENToR S 1M. SY

W C I IR Q on@ UNITED STATES PATENT OFFICE.

WALTER S. MAYER AND WALTER C. KENNEDY, 0F NEW BRIGHTON, PENNSYLVANIA.

i METHOD 0F OXIDIZING MATERIALS IN, ELECTRIC FURNACES.

Specification of Letters Patent.

Application led March 17, 1917. Serial No. 155,383.

To all whom t may concern:

Be it known that we, WALTER S. MAYER and WALTER C. KENNEDY, bothcitizens of the United States, residing at New Brighton, Beaver county,Pennsylvania, have invented a new and useful Improvement in Methods ofOxidizing Materials in Electric Furnaces, of which the following is afull, clear, and exact description, reference being had to theaccompanying drawing, forming part of this specification, in which thefigure illustrates in cross-section, in a diagrammatic and conventionalmanner, the preferred embodiment of the invention.

The present invention relates to electric furnaces and to a method oftreating lnaterials therein.. The object of the invention is to producean electric furnace and a method for oxidizing the materials therein, ashereinafter more fully explained.,

Heretofore,. electric furnaces have been generally constructed toexclude air as far as possible from the furnace chambers, and such airas might leak in has been genen ally regarded as incidental anddisadvantageous. We have found, however, that for certain purposes anelectric furnace should have provision for supplying a certain amount ofoxygen to the materials heated. For'example, in the manufacture of somesteel articles, it is found that in the process of manufacture from theingots the material should have its surface oxidized or scaled.Heretofore, this has usually been accomplished as follows:

The molten steel is first cast in iron molds to form steel ingots. It isfound that the surfaces of these steel ingots are full of surface `pitsor seams. To get a flaw-free surface in the finished articles, thepitted orseamed surface portion must be removed. This is done by thescaling process which takes place during the subsequent heating of theingots and billets. The ingots are heated in gas-fired furnaces calledsoaking pits. The oxidizing atmosphere due to the gas firing oxidizesthe surface of the ingot and thereby removes a part at least of thepitted surface. The heated ingots are then rolled and reduced in crosssection and made into the form ordinarily known as blooms or billets.The blooms or billets are reheated in a second gas-fired furnace inwhich a second scaling occurs with a consequent removal of more of thepitted or seamed surface. AThe heated blooms or bi1- lets are againreduced by rolling. In certaln processes of manufacture, the reduced'billets are again or for a third time heated, and the surface lis thusscaled three times. These successive scaling operations serve toeffectively remove the pitted or seamed surface of the steel occurringin the ingot. ,i One of the objects of the present inventlonls toprovide an electric furnace, in which the requisite scaling of the.ingots or billets may be had, as contrasted with the usual form ofelectric furnace, in which such scaling process does not take place.

By using an electric furnace, the heat canv be accurately controlled,and as the heat is electrically supplied and is independent of the airsupply, the oxidation can be accurately regulated and controlled.

Referring to the drawing, which illustrates in a diagrammatic andconventional manner the preferred embodiment of the invention, thematerial to be heated is shown as billets 1, which are placed in anelectric furnace, indicated generally by the reference numeral 2. Whileany suitable type of furnace may be used, the furnace 2 is illustratedas an electric resistance furnace. The top or arch 3 of the furnace isprovided with a number of resistor units 4, having heated portions 5 atthe interior of the furnace. The external terminals of the resistorelements 4 are provided with electrical connectors 6. The particularform of resistor element is that claimed in our coending applicationSerial No. 137,100, filed ecember 15, 1916. It is to be understood,however, that the inventionis not limited to any particular type offurnace, and any of the well known forms of electric resistance furnacesorelectric arc furnaces may be employed, as will be readily understoodby those skilled in this art.

T he billets 1 are heated to the proper temperature in the furnace. Tooxidize or scale the billets, air is supplied to the furnace chamber 10.As shown in the draw-- ings, the furnace chamber 10 is provided with twopassages 11 and 12, leading thereto and communicating respectively withcheckerwork heat regenerators 13 and 14.

The checkerwork regenerators are connected nectedv with an exhaust 19,leading to a suitable chimney, for example. As-shown in the drawings,the valve 17 is turned so that the blower 18 supplies air through thepassage 16, and checkerwork 14 and the assage 12 to the furnace chamber10. he heated air leaves the 'chamber through the passage 1l, passingthrough and heating the checkerwork chamber/13, and escaping totheatmosphere through the passage 15 and -exhaust.19. The valve 17 isturned to alternately cause the air to pass through the two checkerworkregenerators, thereby preheating the air supplied to the furnacechamber, aswill be readily understood by those skilledQiIl the art.

While it is preferred to preheat the air and to preheat it byregenerators, the air might-be supplied directly to the( furnace. Theair supplied to the furnace Serves to maintain an oxidizing atmospheretherein, giving the requisite scaling` or oxidizing for the materialstherein.

The amount of oxidation can be accurately regulated by controlling theair-supplying blower 18.

While'the preferred embodiment of the invention has been described withparticular reference to the scalini of billets, it is to be understoodthat the invention is not limitedI to its preferred `embodiment nor isit y limited to any particular purpose. For exsists in heating thebillets in an electric furnace to a scaling temperature'while supplyingto the .furnace chamber sufficient oxygen -to form the scale on thebillets, substantially as described.

2. The method of surface oxidizing metal for the. pur oses described,which consists 1n heating t e metal in an electric furnace whllemamtaining an oxidizing atmosphere in the furnace chamber; substantiallyas described.

3. The methodof surface oxidizing metal to remove surface imperfections,which consists in electrically heating the metal to a temperaturesuflicent to scale its surface and supplying a regulated amount ofoxygen to the heated metal suicent to form the surface scale,substantially as described.

4. The method of treating materials for the purposes described, whichconsists in electrically heating the materials and supplylng a regulatedpredetermined amount of oxygen to the heated materials; substantially asdescribedu A5. The method of treating materials for the purposesdescribed, which consists in heating the materials in an electricfurnace, while maintaining .an oxidizing atmosphere in the furnacechamber; substantially as described.

6. The method of scaling steel billets to remove surface imperfections,which consists in heating the billets in an electric furnace to ascaling temperature, supplying to the furnace chamber a suiiicientamount of air to form the scale on the billets, and utilizing theoutgoing) heated air to preheat the incoming air, su stantiallyas'described.

-. 7. The method of treating materials for the purposes described, whichconsists in heating the materials in an electric furnace,

supplying air to the furnace and utilizing the heated outo'oing air topreheat the incoming air; substantially as described.

,In testimony whereof, We have hereunto set our hands.

WALTER s. MAYER. WALTER o. KENNEDY.

